I keep getting these 2 error, no matter what: Error: data and hash arguments required & Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client

I get the first error when comparing hash and plain text. I get the second error in fetchUser.js file when i try to send jwt token in the request headers

Here's my userAuth login route:

router.post('/login', checks.loginChecks, async (req, res) => {
    const errors = validationResult(req);
    if (!errors.isEmpty()) {
        return res.status(400).json({ errors: errors.array() });
    }

    const { email, password } = req.body;

    try {
        let thatOneUser = await User.find({ email });
        console.log(thatOneUser);
        if (!thatOneUser)
            return res.status(403).json({
                success: false,
                message: `Please enter the correct information!`,
            });

        bcrypt.compare(password, thatOneUser.password, (err, result) => {
            if (!result) {
                console.log(err);

                return res.status(403).json({
                    success: false,
                    message: `Please enter the correct information!`,
                    err,
                });
            }
        });

        const authData = { id: thatOneUser.id };
        const authToken = jwt.sign(authData, JWT_SECRET);

        res.json({ success: true, message: 'User has been logged!', authToken });
    } catch (error) {
        res.status(500).json({
            success: false,
            message: 'Error occured during logging the user',
            error,
        });
        console.log(error);
    }
});

and here's my fetchUser.js:

const jwt = require('jsonwebtoken');
const JWT_SECRET = 'jwtsecretabc123';

const fetchUser = (req, res, next) => {
    // Get the user from the jwt token and add id to req object

    const token = req.header('auth-token');
    console.log(token);

    if (!token)
        return res.status(401).json({
            success: false,
            message: 'Please authenticate using a valid token!',
        });

    try {
        const decoded = jwt.verify(token, JWT_SECRET);
        req.user = decoded.user;

        console.log(decoded.user, ' I am decoded id!');

        next();
    } catch (error) {
        return res
            .status(401)
            .json({ success: false, message: 'failed to decode the token' });
    }
};

module.exports = fetchUser;

when i make request to localhost:5000/api/auth/login, it works the first time, but doesn't work the second time.

None of the other requests (register, getUserData) are working either. Any help will be appreciated!